Patent GB-912927-A (GB)
Title: Charge forming apparatus
IPC: F02M17/04
Filed: 1961-01-30
Abstract: 912,927. Charge forming apparatus. TILLOTSON MANUFACTURING CO. Jan. 30, 1961 [Aug. 23, 1960], No. 3407/61. Class 7(3) [Also in Group XXIX] Charge forming apparatus includes a body formed with a mixing passage, an unvented fuel chamber formed in the body, a flexible diaphragm forming a wall of the fuel chamber, a fuel inlet for the fuel chamber, a valve member for the fuel inlet, means establishing operative connection between the valve member and the diaphragm for controlling the position of the valve member for regulating fuel flow from a supply into the fuel chamber, the body being formed with a bore opening into the mixing passage, a fitting pressed into the bore, the fitting having a fuel passage formed therein opening into the mixing passage, a secondary fuel delivery orifice formed in the body opening into the mixing passage and duct means formed in the body for conveying fuel from the fuel chamber to the secondary orifice. Referring to Figs. 1 to 10 the body member 10 is formed with a mixing passage 12 which includes an air inlet region 14 a Venturi 16 and a mixture outlet region 20. The space or chamber 58 is vented to atmosphere through an opening 60 (Fig. 2). The reinforcing member 62 may be of sheet metal or moulded resin. The diaphragm 48 is arranged to regulate the flow of liquid fuel from a supply into the chamber 46. A flexible fuel supply hose or tube (not shown) is connected to the inlet 70. The valve 80 regulates or controls fuel flow into the chamber 46. The fuel chamber 46 is unvented and the diaphragm is flexed solely by asperation or reduced pressure in the mixing chamber 12 set up by air flow through the mixing passage. Comparatively low velocity of air in the mixing passage initiates delivery of fuel through the nozzle 102. The carburetter includes a main nozzle or orifice for high speed operation which is fabricated as a removable unit 102 and a secondary fuel delivery system including engine idling and low speed orifices 106 and 108 respectively. The fuel conveying channels and fuel regulating or metering means for the main orifice and secondary orifice system are illustrated in Figs. 6 and 7. The check valve and main nozzle unit construction 102 is illustrated in Figs. 8 and 9. The main nozzle unit construction 102 is pressed into a bore in the body 10. The valve 112 is a high speed fuel metering valve. The passage 114 is in communication with the recess 98 formed in a wall of the fuel chamber 46 and facilitates fuel flow from the fuel chamber 46 to the main orifice and to the secondary fuel delivery orifices. A passage 116 conveys fuel to the main nozzle 102 and to the secondary orifices 106 and 108. Arranged in parallelism with the passage 116 is a passage or duct 122, the passage 122 being in communication with the chamber 104 of the secondary fuel delivery system through a restricted passage 124. The valve 136 meters or regulates fuel flow to the secondary orifices. The carburetter is operable in various angular positions as well as inverted positions, these conditions being encountered where the carburetter is used with engines powering chain saws. The check valve 156 is preferably fashioned of lightweight material such as nylon or polyoxymethylene resin. In a modification the chamber below the diaphragm is vented to the air inlet region of the mixing passage. In another modification a diaphragm pump is mounted on the carburetter. The pump may be of the character illustrated in Specification 854,216. Modified forms of the main nozzle are shown in Figs. 17 and 18. The valve member 236 may be made of polyoxymethylene phenolformaldehyde resin, polyester resin, polytrifluorochloroethylene or polyamide resin. The carburetter may be used with two stroke cycle and four stroke cycle engines.